The invention relates generally to an apparatus which is to be used in combination with a cigarette or other tobacco product to control sidestream smoke and increase the number of puffs available to the smoker from a given amount of tobacco. The apparatus will permit, for instance, using only as much tobacco as necessary to deliver in a much thinner cigarette of lesser diameter, an increased yield of mainstream smoke from the burning tobacco and conventional taste while significantly reducing sidestream smoke. Unlike a conventional cigarette which involves considerable tobacco waste as the thicker cigarette is burned to produce sidestream smoke, the use of the thinner cigarette with this apparatus converts what would be normally tobacco wasted on sidestream smoke into mainstream smoke.
Simply stated, the apparatus includes a tube having a predetermined porosity into which a tobacco product, such as a cigarette is inserted. Preferably, there is a space between the outside of the cigarette and the inside of the tube. The porosity of the tube is carefully selected to achieve sidestream smoke reduction and reduction of free-burn rate between puffs. A very thin cigarette may be inserted and smoked for the same number of puffs as a conventional cigarette, with the resultant saving of tobacco and other cigarette materials and a significant reduction of sidestream smoke. The tube may include a catalytic material to treat sidestream smoke constituents.
The apparatus will be discussed in greater detail and can be used in various different ways, for instance, rather than a cigarette, a tobacco charge that cannot be separately smoked, is inserted and, by controlling the holes and porosity of the tube, could be smoked. It is apparent that all the conventional quality requirements in making a cigarette, such as, firmness and end fallout are no longer of priority with this invention.
While the apparatus could be sized for use with a conventional cigarette, an advantage is that a thin cigarette can be inserted and smoked with the same smoking characteristics as if it were a conventional sized cigarette.
When smoking in a conventional manner, there is generally understood to be three types of cigarette smoke, mainstream smoke, exhaled smoke and sidestream smoke. There has been significant interest in reducing the amount of sidestream smoke emitted by a burning cigarette or cigar because it accounts for the majority of smoke emitted during the smoking process. Attempts have been made to control sidestream smoke by one or more of the following techniques:
1) alter the tobacco composition and packing characteristics of the tobacco rod or charge in the cigarette or cigar;
2) alter the wrapping for the cigarette or cigar;
3) alter the diameter of the cigarette as well as its tobacco composition; and/or
4) provide a device on the cigarette or cigar to contain and/or control sidestream smoke emissions.
Various cigarette tobacco and cigarette paper formulations have been suggested which in one way or another affect the free-burn rate of the cigarette or cigar with a view to reducing sidestream smoke and/or achieving an extinguishment of the lit cigarette or cigar when left idle over an extended period of time. Such designs include a judicious selection of tobacco blends, density and multiple layers of cigarette tobacco in the tobacco charge. Such selected designs can appreciably retard the free-burn rate of the cigarette and hence, increase the number of puffs obtained per unit length of cigarette. Either in combination with tobacco selection and/or construction or independently of the tobacco make up, various cigarette paper compositions can also affect free-burn rate of the cigarette. Such paper compositions include the use of chemicals to retard free-burn rate, multiple wrappings of different types of cigarette paper of the same or different characteristics and reduction of air permeability. See for example, Canadian Patent 1,259,008 and U.S. Pat. Nos. 4,878,507 and 4,915,117.
Various devices have been provided which contain the cigarette, primarily for purposes of preventing accidental fires. They may or may not at the same time include various types of filters to filter and thereby reduce the amount of sidestream smoke. Examples of such devices are shown in U.S. Pat. Nos. 1,211,071; 3,827,444 and 4,685,477.
Further, various types of cigarette holders have been made available which serve the primary feature of minimizing staining of the smoker""s fingers. Such devices may be connected to the cigarette tip and/or mounted on the cigarette, such as shown in U.S. Pat. No. 1,862,679. Other types of cigarettes which are enclosed in wrappers which are perforated in one way or another to provide for safety features and/or control of sidestream smoke are described in Canadian Patent 835,684 and U.S. Pat. Nos. 3,220,418 and 5,271,419.
Devices which are mountable on the cigarette and which may be slid along the cigarette to control combustion and hence free-burn rate are described in U.K. patent 928,089; U.S. Pat. No. 4,638,819 and International application WO 96/22031. The U.K. patent describes a combustion control device for cigarettes by limiting the flow of air to the cigarette burning ember. By retarding combustion of the cigarette, it is suggested that only half of the conventional amount of tobacco need be incorporated in the cigarette and result thereby in a shorter cigarette. The air flow limiting device may be provided by an array of apertures in the device with variable opening or by crimped portions in the device providing longitudinal openings along part of the cigarette. U.S. Pat. No. 4,638,819 describes a ring which is placed on the cigarette and slid therealong during the smoking process to control the free-burn rate of the cigarette and reduce sidestream smoke. The ring is of solid material, preferably metal, which causes considerable staining and due to variable cigarette diameters cannot reliably provide the desired degree of sidestream smoke reduction and extinguishing times.
An alternative ring system is described in applicant""s published PCT application WO 96/22031. The device is provided with an inner ring which surrounds and contacts a conventional cigarette perimeter where the inner ring is of porous material. The outer ring encases the inner ring to direct air flow along the length dimension of the porous inner ring. The tortuous paths in the porous material of the inner ring controls the rate of air diffusion to the lit cigarette coal and thereby controls the free-burn rate of the cigarette. The porous material enhances the control of sidestream smoke emitted by the lit cigarette. The device may optionally extend up to one-half the length of the cigarette where air would have to flow along the inner porous ring to the burning coal.
Other systems which have been designed to control sidestream smoke are described in published PCT application WO 95/34226 and U.S. Pat. Nos. 5,592,955 issued Jan. 14, 1997 and U.S. Pat. No. 5,105,838 issued Apr. 21, 1992. These references describe various tubular configurations in which a tobacco element is placed in an attempt to minimize cigarette sidestream emission.
Although these approaches may have met with various degrees of success, in controlling sidestream smoke emissions, there are problems with some of the devices in providing conventional taste and flavour, ease of use, ease of manufacture, streamline appearance and significant reductions in the amount of tobacco used. The various embodiments of this invention provide a device which overcomes a number of the above problems by controlling both sidestream smoke and free-burn rate while achieving taste, flavour and constituent deliveries comparable to conventional cigarettes. The device of this invention permits the smoking of a thinner cigarette which has only as much tobacco as is necessary to deliver the desired taste while achieving the conventional number of puffs.
In order to facilitate the description of the invention, the term tobacco charge shall be used in referencing a cigarette, cigar, cigarillo, tobacco rod in a porous mesh, a tobacco plug or wrapped tobacco or the like. It is also understood that where the term cigarette is used, it is interchangeable with cigar, cigarillo and the like.
In accordance with an aspect of the invention, a device for minimizing cigarette sidestream smoke and reducing free-burn rate of a burning cigarette comprises:
i) a non-combustible porous tubular element encasing an effective length of a tobacco charge of a cigarette located in said tubular element, said tubular element having an open end adjacent such cigarette distal end to permit lighting of such cigarette distal end and permits ingress of air; and
ii) the tubular element having a means for both minimizing sidestream smoke emission from a burning tobacco charge and reducing free-burn rate of such burning tobacco charge to increase number of puffs from the burning tobacco charge, the means for minimizing sidestream smoke and reducing free-burn rate comprising a predetermined porosity for the tubular element along at least its length which encases such effective length of a tobacco charge, where the predetermined porosity for the tubular element;
a) retains at least some oxygen deprived combustion gases within the tubular element to minimize release of smoke particles through the openings; and
b) restricts inward flow of air to reduce free-burn rate of a cigarette.
The openings in the tubular element in forming the predetermined porosity may take on various shapes such as narrow slits, slots or pores where the slits and/or slots may be covered with a porous matt of carbon fibre, glass fibre, ceramic fibre, high temperature plastic fibre, metal fibre and the like. The pores may be fabricated in the tubular wall of the element such as by punching to form fibrous projections within the tube where such projections may be relied on to centre a cigarette in the tubular element. Alternatively, the tubular element may comprise a body portion of porous materials which perform the functions of retaining at least some of the oxygen deprived combustion gases within the tube and restrict inward flow of air to reduce free-burn rate of the cigarette.
In accordance with another alternative, the tubular element may be of a heat treated ceramic precursor material which is rendered porous by the heat treatment. The makeup of the ceramic precursor material and the heat treating are carried out in a manner to provide the desired predetermined porosity.
In any of the above devices it is understood that the cigarette may be sufficiently thin to provide an overall dimension for the device which is that of a normal cigarette. The thin cigarette may have a diameter ranging from about 4 to 8 mm and preferably, about 4 to 6 mm and most desirably, about 4 mm. A catalytic material may be incorporated in the tubular element particularly when formed from ceramic. The catalytic material may either be coated on the tubular element or may be activated in the tubular element during heat treating of the ceramic precursor. The catalyst may be selected from a variety of well known groups including those which are based on precious metals and rare earth metals and in particular, based on platinum or cerium.